Clifford D. Simak

American science fiction author and editor Lester del Rey wrote, "Even the devoted aficionado or fan-has a hard time trying to explain what science fiction is," and the lack of a "full satisfactory definition" is because "there are no easily delineated limits to science fiction." According to Isaac Asimov, "Science fiction can be defined as that branch of literature which deals with the reaction of human beings to changes in science and technology." Robert...